A recent Environmental Protection Agency proposal questions long-standing assumptions about the risks of low-level exposure to radiation and toxins.
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As the Environmental Protection Agency (EPA) moves to overhaul how scientific studies can inform regulations, a U.S. Senate panel briefly became a stage for a decades-old scientific argument over the potential human health risks—or benefits—of low doses of toxins and radiation.
EPA’s so-called transparency proposal, released in draft form in April, is contentious because critics say it would bar regulators from considering a wide range of studies that are difficult to reproduce or rest on confidential data, including lengthy, large-scale human health studies involving subjects who were promised privacy. A less discussed provision of the proposal calls on regulators to consider alternatives to their longtime assumption that even small doses of toxins or radiation can pose threats to human health, and that those risks increase as the dose gets bigger—a concept called linear dose-response.
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A scientist who champions an alternative to that model was one of three witnesses at yesterday’s hearing, held by a subcommittee of the Senate Committee on Environment and Public Works. Toxicologist Edward Calabrese of the University of Massachusetts in Amherst, is known for promoting the controversial theory of hormesis—that small doses of toxic agents can be healthful. In 2011, Calabrese sparked outrage by alleging that Hermann Muller and Curt Stern, two researchers who laid the groundwork for modern limits on radiation exposure, had downplayed evidence that radiation was harmless at low levels.
People are constantly exposed to low doses of radiation—from medical procedures, industrial processes, and even food. But how these low doses affect our health and risk of disease is not well understood. As a result, regulators often support a precautionary approach, trying to set limits they think will prevent harm.
Calabrese, however, believes EPA’s approach to dose-response is based on shoddy evidence. It was adopted by “a crusading EPA that was young, impressionable, and inexperienced, and somewhat blinded,” he said in his testimony before the committee. And he praised the agency’s efforts to move away from the default linear dose-response model.
The seven Senators—three Republicans and four Democrats—who attended the low-key, roughly hourlong hearing showed relatively little interest in the dose-response issue, and spent most of their time rehashing well-worn arguments for and against the EPA proposal. In general, both Calabrese and a second witness, economist Robert Hahn of Georgetown University in Washington, D.C., argued the agency should be more transparent about how it uses scientific studies. But Calabrese was more circumspect when it came to key details. Excluding studies from EPA consideration based on whether they can be independently replicated “is not something I would support,” he told reporters after the hearing. “It’s very difficult to ever define what is a truly replicated study.”
The third witness, Rush Holt, CEO of AAAS, which publishes ScienceInsider, was critical of the EPA proposal, which is opposed by a wide range of science groups. It represents an “insidious dodge,” he said, and if adopted will weaken the agency’s ability to protect people from the risk of toxic pollutants.
Holt also was skeptical that EPA’s proposal would lead to a greater acceptance of hormesis. “It’s hard for me to see how [the proposal] would have much affect one way or another on the issue that Ed is concerned about,” he said. “I think it would be a stretch to say it would overturn or even dramatically affect the low-dose debate.”
Calabrese replied, “You may be right.”